Industrial Plant Engineering Practice Test

Condensation starts when moist air is cooled to the temperature at which it becomes saturated with water vapor—the dew point. At a fixed pressure, lowering the air temperature decreases its capacity to hold moisture. When the actual amount of water vapor in the air equals what the air can hold at that temperature, it becomes saturated and the extra vapor condenses into liquid droplets. The dew point thus reflects how much moisture is in the air: more moisture means a higher dew point, while drier air means a lower dew point.

The other terms don’t indicate the condensation temperature: wet-bulb temperature relates to evaporative cooling and depends on humidity; relative humidity is a percentage of saturation, not a temperature; dry-bulb temperature is simply the actual air temperature.